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// Copyright 2015 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/address-map.h"
#include "src/heap/heap.h"
#include "src/isolate.h"
#include "src/objects-inl.h"
namespace v8 {
namespace internal {
RootIndexMap::RootIndexMap(Isolate* isolate) {
map_ = isolate->root_index_map();
if (map_ != nullptr) return;
map_ = new HeapObjectToIndexHashMap();
for (uint32_t i = 0; i < Heap::kStrongRootListLength; i++) {
Heap::RootListIndex root_index = static_cast<Heap::RootListIndex>(i);
Object* root = isolate->heap()->root(root_index);
if (!root->IsHeapObject()) continue;
// Omit root entries that can be written after initialization. They must
// not be referenced through the root list in the snapshot.
// Since we map the raw address of an root item to its root list index, the
// raw address must be constant, i.e. the object must be immovable.
if (isolate->heap()->RootCanBeTreatedAsConstant(root_index)) {
HeapObject* heap_object = HeapObject::cast(root);
Maybe<uint32_t> maybe_index = map_->Get(heap_object);
if (maybe_index.IsJust()) {
// Some are initialized to a previous value in the root list.
DCHECK_LT(maybe_index.FromJust(), i);
} else {
map_->Set(heap_object, i);
}
} else {
// Immortal immovable root objects are constant and allocated on the first
// page of old space. Non-constant roots cannot be immortal immovable. The
// root index map contains all immortal immmovable root objects.
CHECK(!Heap::RootIsImmortalImmovable(root_index));
}
}
isolate->set_root_index_map(map_);
}
} // namespace internal
} // namespace v8
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